- #1

tehmatriks

- 40

- 0

## Homework Statement

simplify (2x-3)² - 2x(2x-5).

## Homework Equations

## The Attempt at a Solution

(2x-3)² - 2x(2x-5)

to

2x² + 9 - 4x² + 10x

to

2x² + 9 + 10x

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- Thread starter tehmatriks
- Start date

- #1

tehmatriks

- 40

- 0

simplify (2x-3)² - 2x(2x-5).

(2x-3)² - 2x(2x-5)

to

2x² + 9 - 4x² + 10x

to

2x² + 9 + 10x

- #2

tiny-tim

Science Advisor

Homework Helper

- 25,838

- 255

sorry, but your (2x-3)² is completely wrong

if you can't do it in your head, write it as (2x-3)(2x-3) first, and then expand it

- #3

tehmatriks

- 40

- 0

sorry, but your (2x-3)² is completely wrong

if you can't do it in your head, write it as (2x-3)(2x-3) first, and then expand it

thanks, the whole time i was staring at the (2x-3)² and was just thinking about how wrong i was doing it, i always forget that double bracket thing when it comes to these situations, just dont get these much

thanks again man, here's the final result

(2x-3)² - 2x(2x-5)

to

(2x-3)(2x-3) - 2x(2x-5)

to

4x - 6x - 6x + 9 - 4x + 10x

to

9 - 2x

- #4

Mark44

Mentor

- 36,342

- 8,297

thanks, the whole time i was staring at the (2x-3)² and was just thinking about how wrong i was doing it, i always forget that double bracket thing when it comes to these situations, just dont get these much

thanks again man, here's the final result

(2x-3)² - 2x(2x-5)

to

(2x-3)(2x-3) - 2x(2x-5)

to

4x - 6x - 6x + 9 - 4x + 10x

to

9 - 2x

Use = between expressions that have the same value.

(2x-3)

= (2x-3)(2x-3) - 2x(2x-5) -- so far, so good

After that, things go downhill.

(2x)(2x) = 2*2*x*x = ?

And -2x(2x - 5) = -2x * 2x -2x * (-5) = ?

You have to distribute the -2x over both terms inside the parentheses.

- #5

tehmatriks

- 40

- 0

Use = between expressions that have the same value.

(2x-3)^{2}- 2x(2x-5)

= (2x-3)(2x-3) - 2x(2x-5) -- so far, so good

After that, things go downhill.

(2x)(2x) = 2*2*x*x = ?

And -2x(2x - 5) = -2x * 2x -2x * (-5) = ?

You have to distribute the -2x over both terms inside the parentheses.

dammit, it's always the simplest of things that i forget

(2x-3)(2x-3) - 2x(2x-5)

to

4x

to -12x + 10x + 9 = 9 - 2x

thanks mark, you're a legend

- #6

Mark44

Mentor

- 36,342

- 8,297

Much better.

The things that you're forgetting are the result of not learning them very well in the first place. If you want to get better at this, I would advise going back and reviewing binomial multiplication (problems like expanding (2x + 3)

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